Methane absorption spectroscopy on a silicon photonic chip

TLDR

Infrared tunable diode‑laser absorption spectroscopy is a key technology for trace‑gas detection in air‑quality monitoring and medical diagnostics, yet conventional sensors rely on discrete optical components that limit large‑scale deployment costs. This work demonstrates IR‑TDLAS on a CMOS‑compatible silicon photonic chip for methane spectroscopy. The system employs a 1650 nm distributed‑feedback laser and an uncooled InGaAs detector to probe the evanescent field of a high‑index contrast nanoscale silicon waveguide, achieving Gaussian‑noise‑limited sub‑100 ppmV detection limits. The results confirm that chip‑scale photonic integration yields compact, cost‑effective, and versatile gas sensors capable of addressing energy and environmental challenges such as natural‑gas leak quantification and fugitive‑emission monitoring.

Abstract

Infrared tunable diode-laser absorption spectroscopy (IR-TDLAS) is an enabling technology for trace-gas detection, with applications ranging from air-quality monitoring to medical diagnostics. However, such sensors typically utilize discrete optical components that pose practical cost limits for large-scale network deployments. Here, we leverage silicon photonics technology to demonstrate IR-TDLAS on an integrated CMOS-compatible platform for methane (CH4) spectroscopy. Using near-IR (1650 nm) light from a distributed-feedback laser and an uncooled InGaAs detector, the evanescent optical field of a high-index contrast nanoscale silicon waveguide is used to probe ambient CH4, yielding Gaussian-noise-limited sub-100 parts-per-million by volume detection limits. Our results demonstrate the feasibility of chip-scale photonic integration for realizing compact, cost-effective, and versatile gas sensors capable of tackling diverse energy and environmental challenges, such as natural-gas leak quantification and localization for fugitive-emissions monitoring.